1. Technical Field
The present disclosure relates generally to patient ventilation systems, and more particularly to a secretion management system and method for a wearable or otherwise portable ventilator in which high frequency pressure/airflow oscillations are selectively generated to mobilize secretions within a patient's respiratory tract.
2. Related Art
The respiration system of the human body provides needed oxygen intake, oxygen/carbon dioxide exchange, and carbon dioxide expulsion functions, each of which involves the lungs. In this regard, the lungs function as a gas-exchanging organ in which inhaled oxygen is passed to the blood, and collected carbon dioxide is passed from the blood to the air. Additionally, the lungs function as a respiratory pump that transports oxygen-rich air into the lungs, and the carbon dioxide-rich air out of the lungs. The breathing center in the brain, central and peripheral nerves, the osseous thorax and the breathing musculature as well as free, stable respiratory paths are necessary for a correct functioning of the respiratory pump.
With patients suffering from certain diseases or other serious medical conditions, there is a constant overload on or exhaustion of the respiratory pump. A typical syndrome is pulmonary emphysema with flat-standing diaphragms without the ability to contract, and the respiratory paths are usually extremely slack and tend to collapse. Consequentially, the patient experiences difficulty with breathing deeply enough and providing the body with needed oxygen while also expelling waste carbon dioxide.
Mechanical ventilators comprise medical devices that either perform or supplement breathing for patients. Conventional ventilators use positive pressure to deliver gas to the patient's lungs via a patient circuit between the ventilator and the patient. The patient circuit typically consists of one or two large bore tubes (e.g., 22 mm inner diameter for adults; 15 mm inner diameter for pediatrics) that interface to the ventilator on one end and a patient mask on the other end. The ventilator applies positive pressure to open the patient's airway to prevent its collapse. In basic implementations, the rate and volume of inhalation and exhalation cycles is set by the ventilator without regard to the patient's spontaneous breathing cycle. However, there are also conventional devices that adjust delivery of ventilation gas based upon patient respiration.
As a part of normal body functioning, mucus is secreted to cover and protect the surface area of the respiratory pathways. It is understood that the clear secretions of mucus trap small debris, pollutants, and particulates as well as infectious disease agents passing through the oral/nasal cavities, pharynx, larynx, trachea, bronchi, and the lungs before it can invade the membranes thereof. In a healthy state, the mucus is expelled by the coordinated and continuous wave-like movement of the ciliated epithelia that line the bronchi and trachea. This movement, also referred to as the mucociliary escalator, pushes up the mucus as far as the junction between the trachea and the larynx, where it may be passed to the esophagus. Excesses that cannot be handled solely by the mucociliary escalator can be removed by coughing.
With the aforementioned weakening of the respiratory system, the ability to expel the mucus may be diminished. However, it is often the case that the infections that are the root causes of diminished respiratory function promote increased production of mucus. The combined effects of more mucus being produced and less of it being expelled through coughing and the action of the mucociliary elevator generally results in the increased retention of mucous within the respiratory tract. This is understood to promote the growth of pathogens, which further exacerbates the condition of the patient. Accordingly, it is expelling mucus from the airways that is critical, particularly for patients suffering from conditions that require breathing augmentation with ventilators, who already have weakened respiratory systems.
One conventional modality for facilitating the removal of mucus from the lungs may be categorized into a genus of like devices all characterized by a valve placed in-line with the patient circuit and is opened and closed rapidly as breathing gas is delivered to the patient. This is understood to induce turbulence or flutter resulting in pressure spikes that promote the movement of mucus. Instead of valves, other oscillating components such as pistons and electromagnetic transducers have also been substituted. Other modalities in which external stimulation of the upper thoracic area is provided in conjunction with the foregoing airway stimulation are also known.
However, these devices may be problematic in a number of different respects. More particularly, conventional devices tend to be ill suited for portable ventilation applications because of the cumbersomeness associated with external components that must be placed along the patient circuit. Furthermore, existing approaches do not have sufficient response characteristics to make high frequency oscillation of the extent necessary for affecting mucus expulsion without complicated vacuum pumps that generate needed reverse pressure for the negative parts of the oscillation. Accordingly, there is a need in the art for an improved wearable ventilator secretion management system.